1. Technical Field of the Invention
The present invention relates to a toner for electrostatic latent image development and an electrostatic latent image developer for electrophotographic devices (for image formation device) such as duplicator, printer and facsimile that are driven according to an electrophotographic process.
The invention also relates to a image formation method.
2. Description of the Related Art
Impurities especially aromatic ingredients with low-molecular weight in toner for electrostatic image development (hereinafter this may be simply referred to as “toner”) that is used in a method of visualization of image information via electrostatic image formation through electrophotography cause some problems in that they often give an offensive odor when toner is used or when a toner container is opened. For toner fixation on copy paper, known are a pressure fixation method and a thermal fixation method. The thermal fixation method includes, for example, oven fixation, flash fixation, pressure fixation, hot roller fixation. In general, hot roller fixation is widely used in electrophotographic duplicators, etc. The method enjoys an extremely high thermal efficiency in fusing a toner image onto a sheet on the surface of a hot roller, and it enables rapid image fixation and is extremely effective in rapid image duplication.
However, the method includes heating a toner image, in which, therefore, minor ingredients in the toner may be released in the air to give an offensive odor to users. With recent down-sizing of duplicators and printers in the art, there is much increasing the opportunity of using them near workers in offices. In addition, there is also increasing the opportunity of using them in ordinary homes. As a result, there are increasing problematic cases where the offensive odor released from toner gives an unpleasant feeling to users. The odor level organoleptically detectable by man is 0.1 ppm or less, and is extremely low.
One cause of offensive odor from electrophotographic devices is ozone generation through corona discharging in the devices, but the ozone smell has been drastically reduced by technological innovation to provide contact charging such as roller charging or brush charging or provide improved corona dischargers capable of preventing ozone generation as much as possible and, as a result, other cases have relatively increased where the toner smell caused by toner gives an unpleasant feeling. A filter or the like to adsorb ozone and odor may be fitted to the body of electrophotographic devices, which, however, is disadvantageous in point of production costs and is troublesome as requiring periodic exchange for its deodorizing function maintenance.
Another method heretofore known for reducing the odor from toner includes reducing the impurities in the binder resin in toner. For example, JP-A-8-328311 proposes odor reduction through reduction in the monomer remaining the binder resin. On the other hand, JP-A-7-104514 says that the reduction in the volatile component in resin is not enough for odor level reduction since the chemically-unstable substance existing as a minor component in the starting material for toner is decomposed during toner production and the resulting volatile substance causes the generation of an offensive odor from toner, and it discloses a technique of removing the odor of the starting material as a measure to solve the odor problem with the final product toner.
JP-A-8-171234 says that the substance to cause odor is an oxidation product of benzaldehyde in toner, and discloses a method of reducing the benzaldehyde content of toner. On the other hand, JP-A-9-230628 discloses a method of reducing the amount of alkylmercaptan (this is one of odor-releasing substances in toner), which is a molecular weight-controlling agent for resin and is indispensable to the basic properties of toner, to the lowermost level necessary for toner so as to prevent odor generation from toner while preventing the toner fixation capability from being worsened.
JP-A-3-105350 discloses a method of adding an alkylbetaine compound to toner in which the compound reacts with odor substances and adsorb them; JP-A-2002-123038 discloses a method of adding any of phyton-cides, catechins or metal phthalocyanines to toner; and JP-A-2002-131980 discloses adding any of macrocyclic lactones or macrocyclic ketone compounds to toner for the purpose of neutralizing the odor of the chain transfer agent in toner resin. In these, however, the compound added inevitably adsorbs some other effective toner component because of its structure, therefore often resulting in that it detracts from the basic quality such as the charging property of toner. JP-A-2-240663 discloses a method of toner deodorization, which includes keeping toner in contact with a deodorant for 5 hours or more in a step of grinding and classifying toner particles. However, the method is still problematic in that it takes a long time to produce toner and it could not always sufficiently reduce the odor of the produced toner.